VERTEBRATE BURROWS WITHIN PEDOGENICALLY MODIFIED DEPOSITS FROM THE LOWER PERMIAN (WOLFCAMPIAN) CEDAR MESA SANDSTONE OF SOUTHEASTERN UTAH, USA

Large- and mega-diameter structures (LS and MS, respectively) have been identified from two locations within the Lower Permian (Wolfcampian) Cedar Mesa Sandstone of southeastern Utah. The two field areas, located in Moki Dugway and the southern portion of Comb Ridge, represent different depositional environments. The Moki Dugway represents an eolian environment, whereas the Comb Ridge section represents a sabkha environment rich in gypsum. The LS and MS have been interpreted as vertebrate burrows and are most common within pedogenically modified eolian and sabkha deposits. The LS and MS are found in association within invertebrate burrows, including Naktodemasis and Planolites, and root traces, including rhizohalos, rhizocretions, and rhizotubules. Invertebrate burrows were commonly found in association with the root traces, representing interactions between plants and the invertebrates that fed off of roots.

The LS are architecturally simple overall. Morphologies observed include: (1) simple, low angle subhorizontal burrows; and (2) shallow, horizontal U-shaped burrows with terminal chamber. The burrows are subhorizontal, with slopes of 10–15 degrees from horizontal, and are elliptical to strongly elliptical in cross section. Diameters of the LS are 5–15 cm wide and 3.5–5 cm high. The LS are exposed at lengths of 30–200 cm and depths of 20–100 cm. The surficial morphology is rarely preserved on the LS. When preserved, they consist of scalloping and longitudinal striations interpreted as scratch marks produced by the tracemaker during excavation. Nodular textures are also preserved on few LS but they are most commonly smooth walled, likely due to weathering.

Unlike the LS, the overall architecture of the MS ranges from (1) simple, low angle subhorizontal burrows and (2) complex shallow branched burrow and chamber complexes. The MS are also subhorizontal and slope 10–20 degrees from the horizontal. The MS are strongly elliptical in cross section with widths of 25–61 cm and heights of 5–12 cm. These burrows reached preserved lengths of up to 150 cm and depths of up to 30 cm. The texture of the burrow walls range from smooth, with no surficial morphologies preserved, to nodular. The varying burrow sizes likely indicate that multiple tracemakers of different sizes and different orders or families were responsible.